Conformal dish



Sept. 16, 1969 M. S. FRANT 3,467,591

' CONFORMAL msu Filed July 25. 1966 so 1 l I V/ 48 3 46 i v I22 3 FIG 2H 58 ,/igo 38 22 I FIG.5 FIG.3 24 I 44 34 22 2 .m v 52 Q FIG.6 l 1 62 wmmv u 4 l i 6 22 2 26 5a i 56 INVENTOR. MARTIN S. FRANT ATTORNEY UnitedStates Patent 3,467,591 CONFORMAL DISH Martin S. Frant, Newton, Mass.,assignor to Orion Research, Inc., Cambridge, Mass., a corporation ofMassachusetts Filed July 25, 1966, Ser. No. 567,605 Int. Cl. B01k 3/00US. Cl. 204-195 4 Claims ABSTRACT OF THE DISCLOSURE This inventionconcerns a dish for holding a minute sample of material for electrolyticanalysis, the dish being formed to have a pair of depressions in the topsurface thereto. The depressions are joined by a channel through which afluid bridge can be formed from one depression to the other. Onedepression is intended to have a standard reference electrode insertedthereon, the second depression being intended to have a specific ionresponsive electrode inserted thereon. Both depressions are shaped toconform to the tip configuration of the respective electrodes. Thesecond depression also includes extending upwardly from the bottom, asmall protuberance which serves to minimize the formation of interferingair bubbles at the ion sensitive surface of the specific ion responsiveelectrode.

This invention relates to electrochemistry and more particularly toapparatus for use in electrochemical analytical procedures involvingliquid samples of limited quantity.

Electrometric determination of ionic activity in solutions usingion-sensitive electrodes is now standard technique, such as inmeasurement of pH. The activity or concentration of a large variety ofions can be measured by similar methods which involve the constructionof a cell of the following general nature:

Electrode reversible to ion X/ solution with ion X/ Salt Bridge/ Ref.electrode.

The reference electrode is usually calomel or Ag-AgCl electrode. Thereversible electrode can be of a large number of diverse electrodes wellknown in the art such as electrodes specific to K Na+, Ca++, H+ or thelike. Both electrodes of the cell generally are in contact with thesolution so that where the electrode configurations provide largecontact surface areas, the amount of solution required is quite largealso. This poses no particular problem in on-stream monitoring of ionactivity in industrial processes generally where conveniently there arelarge quantities of solution. However, in laboratory analyses,frequently very limited sample quantities are available and it is oftenundesirable to increase the amount of solution by dilution because ofdisproportionate changes in ion activity. Also where the activesensitive area of a dipping type electrode is quite large and limited toa substantially flat surface, there is danger of entrapping minute airbubbles against the surface with attendant spurious results in theelectrode EMF developed. For this reason, as described in detail incopending US. application Ser. No. 559,466, filed June 22, 1966, andassigned to the same assignee as the present application, certainelectrodes preferably have at an end to be placed in contact with thesample solution, a concave or dished face surrounding the flation-sensitive area, all edges of the face being rounded. This tends tocause all air bubbles to coalesce and form a large central bubble whichcan be readily removed or washed out.

The principal object of the present invention is to provide a containeror dish for use with an electrochemical analytical cell for holdinglimited amounts of sample solution in operative relation to a pair ofelectrodes. Other ice objects of the present invention are to providesuch a container which is shaped to closely conform to the configurationof the ends of a pair of dipping electrodes of an electrochemicalanalytical cell, thereby minimizing the quantity of sample solutionrequired for a measurement of ion activity in the solution; to provide asolution sample container particularly adapted for use with a firstelectrode having a substantially cylindrically shaped end and a secondelectrode having a substantially concave cup shaped end; and to providesuch a dish which is so inexpensive and simple to make and use as topermit ready discard after a single use, thereby obviating the problemof contamination from sample to sample.

Other objects of the invention will in part be obvious and will in partappear hereinafter. The invention ac cordingly comprises the apparatuspossessing the construction, combination of elements, and arrangement ofparts which are exemplified in the following detailed disclosure, and inthe scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the presentinvention, reference should be had to the following detailed descriptiontaken in connection with the accompanying drawings wherein:

FIG. 1 is a plan view of a conformal dish incorporating the principlesof the present invention;

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 1;

FIG. 4 is a cross-sectional view taken along the line 4-4 of FIG. 1;

FIG. 5 is a side elevational view, partly in fragment, showing a pair ofelectrodes in operative relation to the embodiment of FIG. 1, the latterbeing shown in the same sectional view as FIG. 4; and

FIG. 6 is a front elevational view of the electrode and dish of FIG. 5,the dish being shown in sectional view taken along the line 66 of FIG.1.

Referring now to FIGS. 1 to 4 inclusive, the embodiment of the inventionshown is particularly adapted for use with a pair of dipping electrodesboth of which are cylindrical at the ends thereof intended to contact asample solution, one being truncated by a plane, the other beingtruncated by a concave face. In the form shown, the device of FIG. 1 isa generally block-shaped element '20 having upper surface 22, lowersurface 24, and side surfaces 26, 28, 30 and 32. Upper surface 22includes three depressed portions 34, 36, and 38 all arrangedcontiguously with one another along a common axis. The depressedportions therefore have a common upper edge or lip 40 defined by theintersection of their surfaces with surface 22. Element 20 preferably isformed of waterinsolu ble, imporous, chemically inert (at least to thesample solutions with which it is intended to be used) material,typically glass or a synthetic polymer such as polyvinylchloride whichcan be easily molded or cast.

Depressed portion 34 is substantially scoop-shaped, having its back wall42 concavely curved, substantially cylindrically, with a radius ofcurvature somewhat larger than is necessary to have the wall conform tothe cylindrical end of a dipping electrode of the type describedhereinafter. Front wall 44 of portion 34 is a substantially planesurface sloping at an angle a from a front section of lip 40 to meet thelowest or deepest extremity of wall 42 at an angle to the latterestablished approximately by the conical angle of the electrode end tobe fitted therein. Thus, in section transverse to the common axis, asshown in FIG. 4, portion 34 appears similar to a scoop, back wall 42meeting surface 22 at an angle so that a rear section of lip 40 formedby the intersection of wall 42 and surface 22 is a hemi-oval curve. Theintersection of surface 22 and wall 44 is of course a straight linewhich is preferably parallel to the common axis of the depressedportions.

Portion 36 is similarly scoop-shaped, having its back wall 46 concavelycurved, substantially cylindrically or conically, with a large enoughradius of curvature to conform loosely to a correspondingly cylindricalor conical end of an electrode. The front wall 48 of portion 36 is asubstantially plane surface sloping from the front section of lip 40 tomeet the bottom of the trough configuration of portion 36. This is shownin the section of FIG. 2 wherein it will be seen that back wall 46 andfront wall 48 meet at an angle determined by the conical angle of theelectrode and intended to be inserted in portion 36, i.e. the plane ofwall 48 is normal to the axis of symmetry of wall 46. Front wall 48intersects surface 22, along a line substantially parallel andpreferably colinear with the line of intersection of front wall 44 ofsection 34 with surface 22. Importantly, front wall 48 slopes at thesame angle on with respect to surface 22 as front wall 44.

Positioned substantially centrally in front wall 48 is a smallprotuberance or teat 50 which, as will be explained, serves as astirrer, and is shorter than the depth of the concave face of theelectrode.

Depressed portion 38 is merely a trough or canal which is disposed toprovide fluid communication or a path between portions 34 and 36 andtherefore opens into both the latter.

The operation of the present invention is advantageously described inconjunction with a pair of known electrodes readily availablecommercially. For example, referring to FIGS. 4 and there will be seen apair of electrodes 52 and 54 mounted in operative relation to the dishof the present invention. Electrode 52 is a typical calomel referenceelectrode and characteristically its electrically active exterior is atcylindrical end portion 56. Electrode 54 is a typical electrode of thetype having its active end formed as cone 58 having a dished or concavetruncation 60. This structure is a divalent ion-sensitive electrode issimilar to that hereinbefore referred to in the aforesaid applicationSer. No. 559,466.

In the usual manner, electrodes 52 and 54 are mounted in side by siderelation as in FIG. 6 preferably with the extreme ends of truncation 60and end portion 56 in coplanar relation. Thus, end portion 56 of thereference electrode can be fitted into depressed portion 34 of dishwhilst simultaneously, truncation 60 of the ion-sensitive electrode isfitted into depressed portion 36. It will be seen that the depressedportions are dimensioned to be slightly larger than the correspondingelectrode tips so that a small interspace is left through which samplesolution can flow. Clearly, very small quantities of sample solution,e.g. 1 ml. or even less, suffice to fill such interspace and provideionic communication between the electrodes while contacting the entireactive surfaces of the electrodes.

In order to insure that air does not become entrapped with the concavityof truncation 60 or against the fiat bottom of cylindrical end portion56, it is preferred to mount the two electrodes so that their long axesform the angle a with respect to vertical (assuming surface 22 dish 20is to be the horizontal). Thus, the bottom faces of the electrode endsare parallel to surfaces 48 and 44 when inserted into dish 20. The angleor is determined primarily by the edge angle of the concavity oftruncation 60 of a particular electrode with which dish 20 is to beused. For example, if the portion of the concavity of truncation 60(which is usually rotationally symmetrical about an axis which iscolinear with the longitudinal axis of the electrode) adjacent an edgethereof forms an angle 5 with respect to that longitudinal axis, then ashould be about the complement of B. Usually, ,8 is between about 60 to75, hence a should lie in the range of about 15 to It will be apparentthat if the electrodes are mounted at angle a to the vertical, edgeportion of the concavity of truncation 60 will be quite horizontal. Ifactually a is a few degrees greater than the complement of 13, the edgeportion of the concavity will slant upwardly from the horizontal. Ineither case, air bubbles in the concavity will tend to slide out or beeasily removed. This can be efl'ected simply by gently moving or shakingthe dish and electrodes relative to one another that teat 50 can act asa stirrer and engage such bubbles or create eddies either of which willtend to force the bubbles out of the concavity of truncation 60.

While the present invention has been described in conjunction with areference dipping electrode having a cylindrical tip shape, it will beobvious to those skilled in the art that the configuration of dish 20can be modified to allow depressed portion 34 to conform to other tipshapes such as conical, spherical or the like.

Similarly dish 20 need not be a solid block but can be hollowedunderneath in the portions thereof not depressed, thus reducing theamount of materials used. Although in the form shown, for the sake ofstability, dish 20 includes bottom lip flange 62 surrounding the dishand substantially coplanar with bottom surface 24, the device need nosuch flange and indeed can be mounted in a number of otherconfigurations (e.g. with legs) so as that surface 22 can be keptsubstantially horizontal when in use.

Since certain changes may be made in the above apparatus withoutdeparting from the scope of the invention herein involved it is intendedthat all matter contained in the above description or shown in theaccompanying drawing shall be interpreted in an illustrative and not ina limiting sense.

What is claimed is:

1. A container for sample solution, ionic activity of which is to bedetermined by a pair of elongated dipping electrodes immersed therein,one of said electrodes being an electrode of the type having an endwhich is concavely dished, said container comprising, in combination;

an element having a top surface with at least two separated, depressedportions therein, each of said depressed portions having a forward wallin the form of a corresponding plane surface sloping downwardly in thesame direction and at substantially the same angle from said top surfacetoward the depth of the respective depressed portion, each depressedportion having an arcuate back wall connected adjacent said depth to thecorresponding forward wall; and

a channel in said top surface for providing a fluid path between saiddepressed portions.

2. A container as defined in claim 1 including a protuberancesubstantially centrally located in the plane surface of one of saiddepressed portions.

3. A container as defined in claim 1 wherein said angle is one in therange of from 15 to 30 from said top surface.

4. A container as defined in claim 1 wherein each plane surface isdisposed at an angle approximately normal to the axis of symmetry of thecorresponding back wall.

References Cited UNITED STATES PATENTS 2,499,852 3/1950 Dietz 204195.12,838,233 6/1958 Garrison 204- 3,055,759 9/1962 Busby et al. 204-1953,222,269 12/1965 Stanton 204-242 JOHN H. MACK, Primary Examiner T.TUNG, Assistant Examiner US. Cl. X.R.

